This invention relates to an apparatus for making a web comprising thermoplastic synthetic resin fibers.
Japanese Patent Application Publication No. 1973-38025B discloses an invention entitled “Process and apparatus for making nonwoven sheet- and fleece-like fibrous assembly from a plurality of melt spun single yarn filaments”. According to this invention, a web comprising a plurality of melt spun continuous filaments is obtained in a form of fabricated fibers. The filaments are guided into a sucker located at a lower side of a melt extruder by a distance sufficient to solidify the filaments before entering the sucker. Inside the sucker, air-jet-flow acts on both sides of a plurality of the filaments arrayed along the longitudinal direction of the sucker so that the filaments may be cooled and stretched as these filaments are sent to the lower side of the sucker. Immediately below the sucker, a collecting belt runs upon which a plurality of the filaments are assembled to form the fabricated fibers in a form of spun bond nonwoven fabric or the like.
U.S. Pat. No. 5,439,364 discloses an apparatus for making a fibrous web comprising a plurality of continuous filaments. In the case of this apparatus, a plurality of filaments extruded from a plurality of nozzles of an extruder and arrayed in a line are quenched and then introduced into a drawing off passage through its rectangular upper end opening. A lower end opening of this drawing off passage is in contact with a peripheral surface of a rotary drum having a plurality of openings on the peripheral surface. In the drawing off passage, suction induced from inside the rotary drum is exerted not only at its lower end but also at its intermediate region defined between the upper and lower end openings so that the filaments may be accumulated on the peripheral surface of the rotary drum after introduced into the drawing off passage. The drawing off passage is structured to be narrow in its width in a rotational direction of the drum in the vicinity of the upper end opening and abruptly enlarged in the vicinity of the lower end opening.
The problem common to the above-cited inventions is to distribute a plurality of filaments as evenly as possible in the longitudinal direction as well as in the transverse direction of the collecting belt serving as a conveying means for the web and the rotary drum without locally intertwined in many layers and thereby to obtain the fibrous web in which the fibers are uniformly distributed. However, in the apparatus disclosed in Japanese Patent Application Publication No. 1973-38025B, the sucker and the collecting belt running immediately below the sucker are separated each other only by a distance h2 and the air ejected from the narrow lower end of the sucker may generate a turbulent flow of air in a gap defined by this distance h2. Such turbulent flow of air may prevent the filaments from being evenly distributed.
In the case of the apparatus disclosed in U.S. Pat. No. 5,439,364, the drawing off passage is subjected, in the vicinity of its upper end opening, to the suction effect provided from the interior of the rotary drum and from the intermediate region but, in the region lower than the intermediate region, to the suction effect provided from the interior of the rotary drum. In consequence, the suction effect is relatively weak in this lower region. The filaments introduced into the drawing off passage descend at a correspondingly reduced velocity in the region lower than the intermediate region and are evenly received on the peripheral surface of the rotary drum. In this manner, this apparatus of well known art requires double suction system, one provided from the rotary drum and the other provided from the intermediate region. This requirement necessarily complicates the apparatus and operational control of the apparatus.